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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC Sierra Denali 🢒 Body 🢒 Body Front End 🢒 Thermostat Housing Crossover Replacement

Thermostat Housing Crossover Replacement 6.6L (LLY) Engine

Removal Procedure

    Object Number: 674573 Size: SH
  1. Remove the intake manifold cover. Refer to Intake Manifold Cover Replacement for the 6.6L (LLY) engine.
  2. Drain the cooling system. Refer to Cooling System Draining and Filling .
  3. Disconnect the negative battery cables. Refer to Battery Negative Cable Disconnection and Connection .
  4. Remove the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .
  5. Remove the drive belt. Refer to Drive Belt Replacement for the 6.6L (LLY) engine.
  6. Disconnect the air conditioning (A/C) compressor clutch electrical connector (5).
  7. Disconnect the A/C cut out switch electrical connector.

    8. Object Number: 652573 Size: SH
  8. Remove the A/C compressor bolts.
  9. Reposition the A/C compressor, with the hoses attached, to the right side of the engine compartment.

    10. Object Number: 1409332 Size: SH
  10. Remove the generator positive cable to generator nut.
  11. Remove the positive cable from the generator.
  12. Remove the clip holding the positive cable to the engine front cover.
  13. Remove the battery positive cable junction block to power steering pump bolt (1).
  14. Move the generator positive cable and the junction block bracket aside.

    15. Object Number: 1335413 Size: SH
  15. Disconnect the generator electrical connector.
  16. Disconnect the engine coolant temperature (ECT) sensor electrical connector.

    17. Object Number: 1602063 Size: SH
  17. Remove the air conditioning (A/C) compressor/power steering pump bracket bolts.
  18. Reposition the A/C compressor/power steering pump bracket and secure to the side.
    19. • Do not remove the power steering pump from the bracket.
    • The hoses and battery cables can remain on the power steering pump.

    Object Number: 1334912 Size: SH
  19. Remove the heater outlet hose bracket bolt from the generator bracket.
  20. Remove the idler pulley.
  21. Remove the generator bracket bolts.
  22. Remove the generator bracket and position to the side.
    23. • The generator does not require removal.
    • The drive belt tensioner does not require removal.
  23. Remove the oil fill tube. Refer to Oil Filler Tube Replacement for the 6.6L (LLY) engine.
  24. Remove the water outlet. Refer to Water Outlet Tube Replacement .

    25. Object Number: 1335419 Size: SH
  25. Reposition the exhaust gas recirculation (EGR) hose clamp at the EGR coolant pipe.
  26. Remove the EGR coolant pipe bolt.
  27. Remove the EGR coolant pipe with O-ring seal from the crossover.

    28. Object Number: 1335429 Size: SH
  28. Reposition the turbocharger coolant return pipe hose clamp.
  29. Remove the turbocharger coolant return pipe hose.

    30. Object Number: 1335434 Size: SH
  30. Remove the fuel line bracket bolt at the thermostat housing crossover.
  31. Remove the cooling fan pulley. Refer to Cooling Fan Pulley Replacement .

    32. Object Number: 1335424 Size: SH
  32. Remove the water pump inlet pipe bolts.

    33. Object Number: 1335441 Size: SH
  33. Remove the thermostat housing bolts and nuts.
  34. Remove the thermostat housing, with the bypass pipe.
  35. Remove and discard the thermostat bypass pipe to water pump O-ring seal.
  36. Remove and discard the thermostat housing gaskets.
  37. If necessary, perform the following steps:
    38. 37.1. Remove the thermostat bypass pipe from the thermostat housing.
    37.2. Remove and discard the thermostat bypass pipe O-ring seal.
    37.3. Remove the thermostat cover bolts and cover.
    37.4. Remove the thermostats.
    37.5. Remove and discard the thermostat seals.
  38. If required, clean and inspect the thermostat housing. Refer to Engine Coolant Thermostat Housing Cleaning and Inspection for the 6.6L (LLY) engine.

Installation Procedure

    Object Number: 1335441 Size: SH
  1. If necessary, perform the following steps:
    2. 1.1. Install NEW seals to the thermostats.
    1.2. Install the thermostats.

    Notice: Refer to Fastener Notice in the Preface section.

    1.3. Install the thermostat cover and bolts.

    Tighten
    Tighten the bolts to 21 N·m (15 lb ft).

    1.4. Install a NEW O-ring seal to the thermostat bypass pipe.
    1.5. Install the thermostat bypass pipe to the thermostat housing.
  2. Install a NEW thermostat bypass pipe to water pump O-ring seal.
  3. Install the thermostat housing using NEW gaskets.
  4. Install the thermostat housing bolts and nuts

    5. Tighten
    Tighten the bolts/nuts to 21 N·m (15 lb ft).


    Object Number: 1335424 Size: SH
  5. Install the water pump inlet pipe bolts.

    6. Tighten
    Tighten the bolts to 21 N·m (15 lb ft).

  6. Install the cooling fan pulley. Refer to Cooling Fan Pulley Replacement .

    7. Object Number: 1335434 Size: SH
  7. Install the fuel line bracket bolt at the thermostat housing crossover.

    8. Tighten
    Tighten the bolt to 21 N·m (15 lb ft).


    Object Number: 1335429 Size: SH
  8. Install the turbocharger coolant return pipe hose.
  9. Position the turbocharger coolant return pipe hose clamp.

    10. Object Number: 1335419 Size: SH
  10. Install the EGR coolant pipe with O-ring seal to the crossover.
  11. Install the EGR coolant pipe bolt.

    12. Tighten
    Tighten the bolt to 25 N·m (18 lb ft).

  12. Position the EGR hose clamp at the EGR coolant pipe.
  13. Install the water outlet. Refer to Water Outlet Tube Replacement .
  14. Install the oil fill tube. Refer to Oil Filler Tube Replacement for the 6.6L (LLY) engine.

    15. Object Number: 1334912 Size: SH
  15. Position the generator bracket.
  16. Install the generator bracket bolts.

    17. Tighten
    Tighten the bolt to 50 N·m (37 lb ft).

  17. Install the idler pulley.

    18. Tighten
    Tighten the bolt to 43 N·m (32 lb ft).

  18. Install the heater outlet hose bracket bolt to the generator bracket.

    19. Tighten
    Tighten the bolt to 21 N·m (15 lb ft).


    Object Number: 1602063 Size: SH
  19. Position the A/C compressor/power steering pump bracket.
  20. Install the A/C compressor/power steering pump bracket bolts.

    21. Tighten
    Tighten the bolt to 46 N·m (34 lb ft).


    Object Number: 1409332 Size: SH
  21. Position the generator positive cable and the junction block bracket.
  22. Install the battery positive cable junction block to power steering pump bolt (1).

    23. Tighten
    Tighten the bolt to 9 N·m (80 lb in).

  23. Install the clip holding the positive cable to the engine front cover.
  24. Install the positive cable to the generator.
  25. Install the generator positive cable to generator nut.

    26. Tighten
    Tighten the nut to 9 N·m (80 lb in).


    Object Number: 1335413 Size: SH
  26. Connect the ECT sensor electrical connector.
  27. Connect the generator electrical connector.

    28. Object Number: 652573 Size: SH
  28. Position the A/C compressor, with the hoses attached.
  29. Install the A/C compressor bolts.

    30. Tighten
    Tighten the bolts to 50 N·m (37 lb ft).


    Object Number: 674573 Size: SH
  30. Connect the A/C cut out switch electrical connector.
  31. Connect the A/C compressor clutch electrical connector (5).
  32. Install the drive belt. Refer to Drive Belt Replacement for the 6.6L (LLY) engine.
  33. Install the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .
  34. Connect the negative battery cables. Refer to Battery Negative Cable Disconnection and Connection .
  35. Fill the cooling system. Refer to Cooling System Draining and Filling .
  36. Install the intake manifold cover. Refer to Intake Manifold Cover Replacement for the 6.6L (LLY) engine.